Wanting to get first classic Mopar

Short of being a pro basketball player, I don't think you will find a major issue with room in an A-body or B-body. If you came to this forum, I would assume you have interest in possibly an A-body as your choice. You definitely can't go wrong with that. Not that you can really go wrong with any Mopar.

And welcome to the forum from Fredericksburg, VA.